Heat oven to 375 degrees F. Melt butter and then sauté the onion and garlic until tender. Add the flour. Mix well.

Gradually add the milk, stirring constantly. Cook until the sauce thickens. Add the sherry and the seasonings to taste. In a separate bowl, combine shrimp, mushrooms, eggs, and parsley. Add sauce along with 1/4 cup cheese to shrimp mixture.

Mix well. Pour the mixture into a 2-quart casserole dish and top with remaining cheese. Dot with the butter.